A method of manufacturing a lithium-ion secondary battery is disclosed in, for example, Patent Literature 1, JP 1998-302774 A, in which graphite powder in a paste form is coated onto a copper foil and thereafter dried to obtain an electrode as a negative electrode. According to this publication, an electrode with the same structure is obtained also as the positive electrode. Then, the negative electrode, a separator, the positive electrode, and a separator are stacked in that order, and these are coiled in a cylindrical shape, to thereby prepare a wound electrode assembly. The wound electrode assembly and an electrolyte solution are placed into a battery case, whereby a battery is fabricated.
The just-mentioned Patent Literature 1 proposes the use of graphite powder having a powder bulk density of 0.5 g/cm3 and an oil absorption number of 65 (mL/100 g), for the graphite powder used as the negative electrode active material.
Patent Literature 2, IP 2004-265754 A, discloses the use, as a negative electrode active material, of a composite carbon material in which the surfaces of carbonaceous particles serving as the core are coated with amorphous carbon. It is disclosed therein that the coating amount of the amorphous carbon is set to be from 0.1 mass % to 15.0 mass % with respect to the mass of the carbonaceous particles serving as the core. It is also disclosed that the content of the composite carbon material should be set at 30 mass % or greater with respect to the mass of the negative electrode active material.
Patent literature 3, IP 2005-294011 A, proposes the use of a mixture of graphite particles the surfaces of which are not coated with amorphous carbon and graphite particles the surfaces of which are coated with amorphous carbon, for the graphite particles contained as the active material in the negative electrode. It also proposes that in the graphite particles the surfaces of which are coated with amorphous carbon, the mass of the amorphous carbon is 0.1 parts to 10 parts by mass.
Patent Literature 4, JP 2009-211818 A, uses, as the negative electrode active material of a non-aqueous electrolyte secondary battery, particles in which the surfaces of graphite particles are coated with amorphous carbon and the coating amount thereof is 0.1 mass % to 10 mass % with respect to the amount of graphite. It is proposed therein to use, as the amorphous carbon, a substance having a specific surface area of from 200 m2/g to 500 m2/g, when sintered alone, and having a molecular weight of from 300 to 500.